Physiological stress detector device and method

Abstract

A method and device for measurement of a level of at least one blood constituent. The device includes a light source and a light detector proximate the surface of an organ. The device also includes a pair of adjustable gain amplifiers and a processor/controller connected within a processing unit. The processing unit operates to separate an AC signal component from a DC signal component. The light source includes at least one light emitting unit. Preferably, the light source alternatingly emits light at two different wavelength ranges and normalizes the AC and DC output signals corresponding with the intensity of the light reflected from the organ and calculates a ratio of the normalized signals for each wavelength range. The device may determine the level of the blood constituent and may also use this level for monitoring and/or to activate an alarm when the level falls outside a predetermined range. The device and the method may be applied to monitoring, inter alia, conditions of apnea, respiratory stress, reduced blood flow in organ regions, heart rate, jaundice, and blood flow velocity.

What is claimed is:  
     
       1. A non-invasive device disposed proximate a surface of an organ for measurement of a level of at least one blood constituent, comprising: 
       at least one light source, providing light directed toward said surface of said organ, the light being reflected from said organ;  
       a light detector spaced apart from said at least one light source and being sensitive to intensity levels of said reflected light for producing intensity signals in accordance therewith; and  
       a processing unit for processing said intensity signals received from said light detector, said processing unit comprising:  
       first and second amplifiers for amplifying said intensity signals, each in accordance with a respective first and second gain amplification factor; and  
       a processor for automatically determining said first and second gain amplification factors in adjustable fashion;  
       wherein during a first stage, said first and second amplifiers amplify a DC signal component of said intensity signals in accordance with predetermined first and second gain amplification factors, and wherein the amplified DC signal component is converted by a digital to analog converter to an analog signal and is subtracted from the intensity signals, said amplified DC signal component being subtracted from said intensity signals at an input of said first amplifier, to isolate an AC signal component of said intensity signals,  
       and wherein during a second stage, said second amplifier amplifies said isolated AC signal component in accordance with said adjustably-determined second gain amplification factor,  
       said processing unit producing output signals in accordance with said isolated AC signal component and said DC signal component and calculating in accordance therewith, at least one blood constituent level.  
     
     
       2. The device according to  claim 1  wherein said processor develops a control signal when said adjustably-determined second gain amplification factor is established in said second stage, said control signal is able to shut off said light source. 
     
     
       3. The device according to  claim 2  wherein said control signal conserves energy by reducing an operational duty cycle of said at least one light source. 
     
     
       4. The device according to  claim 1  wherein said at least one light source comprises a single light emitting unit capable of controllably providing light having a wavelength range selected from at least a first wavelength range and a second wavelength range, said first wavelength range being at least partially different from said second wavelength range, said single light emitting unit can be switched from emitting light within said first wavelength range to emitting light within said second wavelength range. 
     
     
       5. The device according to  claim 1  wherein said at least one light source provides light having wavelengths in the red and infrared ranges. 
     
     
       6. The device according to  claim 5  wherein said organ is the skin, said blood constituent is hemoglobin, and wherein measurement of a level of oxygen saturation in said hemoglobin provides an early indication of respiratory stress. 
     
     
       7. The device according to  claim 6  wherein said respiratory stress is associated with Sudden Infant Death Syndrome. 
     
     
       8. The device according to  claim 6  used to monitor heart rate. 
     
     
       9. The device according to  claim 6  used as an apnea monitor. 
     
     
       10. The device according to  claim 6  wherein the device is a portable hand held reflective pulse oximeter. 
     
     
       11. A non-invasive device disposed proximate a surface of an organ for measurement of a level of at least one blood constituent, comprising: 
       at least one light source, providing light directed toward said surface of said organ, the light being reflected from said organ;  
       a light detector spaced apart from said at least one light source and being sensitive to intensity levels of said reflected light for producing intensity signals in accordance therewith; and  
       a processing unit for processing said intensity signals received from said light detector, wherein processing the intensity signals is done through a single analog path, said processing unit comprising:  
       first and second amplifiers for amplifying said intensity signals, each in accordance with a respective first and second gain amplification factor; and  
       a processor for automatically determining said first and second gain amplification factors in adjustable fashion;  
       wherein during a first stage, said first and second amplifiers amplify a DC signal component of said intensity signals in accordance with predetermined first and second gain amplification factors, said amplified DC signal component being subtracted from said intensity signals at an input of said first amplifier, to isolate an AC signal component of said intensity signals,  
       and wherein during a second stage, said second amplifier amplifies said isolated AC signal component in accordance with said adjustably-determined second gain amplification factor,  
       said processing unit producing output signals in accordance with said isolated AC signal component and said DC signal component and calculating in accordance therewith, at least one blood constituent level.  
     
     
       12. The device according to  claim 11  wherein said at least one light source comprises a single light emitting unit capable of controllably providing light having a wavelength range selected from at least a first wavelength range and a second wavelength range, said first wavelength range being at least partially different from said second wavelength range, said single light emitting unit can be switched from emitting light within said first wavelength range to emitting light within said second wavelength range. 
     
     
       13. The device according to  claim 11  wherein said processor develops a control signal when said adjustably-determined second gain amplification factor is established in said second stage, said control signal is able to shut off said light source. 
     
     
       14. The device according to  claim 13  wherein said control signal conserves energy by reducing an operational duty cycle of said at least one light source. 
     
     
       15. The device according to  claim 11  wherein said at least one light source provides light having wavelengths in the red and infrared ranges. 
     
     
       16. The device according to  claim 15  wherein said organ is the skin, said blood constituent is hemoglobin, and wherein measurement of a level of oxygen saturation in said hemoglobin provides an early indication of respiratory stress. 
     
     
       17. The device according to  claim 16  wherein said respiratory stress is associated with Sudden Infant Death Syndrome. 
     
     
       18. The device according to  claim 16  used to monitor heart rate. 
     
     
       19. The device according to  claim 16  used as an apnea monitor. 
     
     
       20. The device according to  claim 16  wherein the device is a portable hand held reflective pulse oximeter. 
     
     
       21. The device according  claim 1  or  11  wherein said at least one light source and said light detector are held in a spaced relationship while in contact with the surface of said organ so as to substantially block entrance of external light therebetween. 
     
     
       22. The device according to  claim 1  or  11  wherein said processing unit further comprises: 
       means for normalizing said output signals to produce first and second normalized signals; and  
       means for forming a ratio of said first and second normalized signals, said processor calculating said blood constituent level in accordance with said ratio.  
     
     
       23. The device according to  claim 1  or  11  wherein said organ is the skin and said device is arranged for mounting on a ribbon or a bracelet for placement on a part of a human or an animal body. 
     
     
       24. The device according to  claim 1  or  11  wherein said organ is the skin and said device is arranged for mounting on a tightly-fitted garment to be worn over a part of the body. 
     
     
       25. The device according to  claim 1  or  11  further comprising a transmitter for transmitting said output signals to a receiver at a remote location, allowing monitoring of said at least one blood constituent level from said remote location, 
       said receiver being equipped with an alarm unit for alerting when said at least one blood constituent level falls outside of a predetermined range.  
     
     
       26. The device according to  claim 1  or  11  wherein said first and second gain amplification factors are determined by said processor in an iterative process by adjustably setting a gain amplification factor and measuring a dynamic voltage range of said output signals to determine if said voltage range falls within a predetermined window established by said processor. 
     
     
       27. The device according to  claim 1  or  11  wherein said light source comprises at least a first light emitting unit capable of controllably emitting light having a first wavelength range and a second light emitting unit capable of controllably emitting light having a second wavelength range, said first wavelength range being at least partially different from said second wavelength range. 
     
     
       28. The device according to  claim 1  or  11  wherein said output signals are sent by said processor to an alarm unit for alerting when said at least one blood constituent level falls outside of a predetermined range. 
     
     
       29. The device according to  claim 1  or  11  adapted to determine blood bilirubin levels. 
     
     
       30. The device according to  claim 1  or  11  used for mapping the intensity of said AC signal component along the surface of said organ to detect regions of said organ having a reduced blood flow. 
     
     
       31. A method for measurement of a level of at least one blood constituent, the method comprising the steps of: 
       providing light from at least one light source disposed proximate a skin surface, directing said light toward the skin surface, said light being reflected from said skin surface;  
       providing a light detector spaced apart from said at least one light source and being sensitive to intensity levels of said light reflected from said skin for producing intensity signals in accordance therewith;  
       processing said intensity signals received from said light detector, said processing step comprising the steps of:  
       amplifying said intensity signals in first and second amplifiers, each in accordance with a respective first and second gain amplification factor; and  
       automatically determining said first and second gain amplification factors in adjustable fashion;  
       wherein during a first stage, said first and second amplifier amplify a DC signal component of said intensity signals in accordance with predetermined first and second gain amplification factors, and wherein the amplified DC signal component is subtracted from the intensity signals by a digital to analog converter, said DC signal component being subtracted from said intensity signals at an input of said first amplifier, thereby isolating an AC signal component of said intensity signals, and  
       wherein during a second stage, said second amplifier amplifies said isolated AC signal component in accordance with said adjustably-determined second gain amplification factor, said processing step producing output signals in accordance with said isolated AC signal component and said DC signal component; and  
       calculating in accordance therewith, said at least one blood constituent level, wherein the amplified DC signal component is converted by a digital to analog converter to an analog signal and is subtracted from the intensity signals.  
     
     
       32. The method according to  claim 31  wherein the processing is a serial process. 
     
     
       33. The method according to  claim 32  wherein said blood constituent is hemoglobin, the method further comprising the step of measuring a level of oxygen saturation in said hemoglobin providing an early indication of respiratory stress. 
     
     
       34. The method according to  claim 33  wherein said respiratory stress is associated with Sudden Infant Death Syndrome. 
     
     
       35. The method according to  claim 32  further comprising the step of initiating an alarm for alerting when said at least one blood constituent level falls outside of a predetermined range. 
     
     
       36. The method according to  claim 35  wherein said alarm is selected from an audible alarm, a visual alarm, a tactile alarm, dialing a telephone number and any combination thereof. 
     
     
       37. The method according to  claim 32  wherein said light is alternatingly selected from at least a first wavelength range and a second wavelength range, said first wavelength range being at least partially different from said second wavelength range. 
     
     
       38. The method according to  claim 37  wherein said first wavelength range includes wavelength of red light and said second wavelength range includes wavelength of infra-red light, said at least one blood constituent is hemoglobin and wherein said method determines a level of oxygen saturation of said hemoglobin. 
     
     
       39. The method according to  claim 38  used for monitoring heart rate. 
     
     
       40. The method according to  claim 38  used for monitoring a condition of apnea. 
     
     
       41. The method according to  claim 38  further including the step of repeating said steps of providing light, providing a light detector and processing, at a plurality of positions along said skin for mapping the levels of said AC signal component along the surface of said skin to detect regions of reduced blood flow. 
     
     
       42. The method according to  claim 31  further comprising the step of initiating an alarm for alerting when said at least one blood constituent level falls outside of a predetermined range. 
     
     
       43. The method according to  claim 42  wherein said alarm is selected from an audible alarm, a visual alarm, a tactile alarm, dialing a telephone number and any combination thereof. 
     
     
       44. The method according to  claim 31  wherein said light is alternatingly selected from at least a first wavelength range and a second wavelength range, said first wavelength range being at least partially different from said second wavelength range. 
     
     
       45. The method according to  claim 44  wherein said first wavelength range includes wavelength of red light and said second wavelength range includes wavelength of infra-red light, said at least one blood constituent is hemoglobin and wherein said method determines the level of oxygen saturation of said hemoglobin. 
     
     
       46. The method according to  claim 45  used for monitoring heart rate. 
     
     
       47. The method according to  claim 45  used for monitoring a condition of apnea. 
     
     
       48. The method according to  claim 45  further including the step of repeating said steps of providing light, providing a light detector and processing, at a plurality of positions along said skin for mapping levels of said AC signal component along the surface of said skin to detect regions of reduced blood flow. 
     
     
       49. The method according to  claim 31  or  32  further comprising the step of transmitting said output signals to a receiver at a remote location, allowing monitoring of said at least one blood constituent level from said remote location, said receiver being equipped with an alarm unit for alerting when said at least one blood constituent level falls outside of a predetermined range. 
     
     
       50. The method according to  claim 31  or  32  wherein said step of processing further comprises: 
       normalizing said output signals to produce first and second normalized signals;  
       forming a ratio of said first and second normalized signals; and  
       calculating said blood constituent level in accordance with said ratio.  
     
     
       51. The method according to  claim 31  or  32  further comprising the steps of: 
       developing a control signal when said adjustably-determined second gain amplification factor is established in said second stage; and  
       shutting off said at least one light source in response to said control signal.  
     
     
       52. The method according to  claim 31  or  32  further comprising the steps of: 
       determining said first and second gain amplification factors by a processor in an iterative process by adjustably setting a gain amplification factor; and  
       measuring a dynamic voltage range of said output signals to determine if said voltage range falls within a predetermined window established by said processor.  
     
     
       53. The method according to  claim 31  wherein said blood constituent is hemoglobin, the method further comprising the step of measuring a level of oxygen saturation in said hemoglobin providing an early indication of respiratory stress. 
     
     
       54. The method according to  claim 53  wherein said respiratory stress is associated with Sudden Infant Death Syndrome. 
     
     
       55. The method according to  claim 31  or  32  used for monitoring a level of bilirubin in blood. 
     
     
       56. A method for non-invasively determining blood flow velocity in a region of an organ, the method comprising the steps of: 
       positioning a first pulse-oximetry device and a second pulse-oximetry device proximate a surface of said region, said first and said second device being separated from each other by a predetermined distance;  
       simultaneously obtaining a first and a second sets of data representing pulsatile variation of a level of oxygen saturation at locations of said first and said second device, respectively, as a function of time, each of said first set and second set of data including at least one extremum data value, said at least one extremum data value of said first set of data corresponding to said at least one extremum data value of said second set of data;  
       calculating the time interval between said at least one extremum data value of said first set of data and said at least one extremum data value of said second set of data;  
       dividing the value of said predetermined distance by the value of said time interval to obtain a value representing the approximate blood flow velocity in said region of said organ,  
       wherein each of said first device and said second device includes:  
       at least one light source, providing light directed toward the surface of said organ, said light being reflected from said organ;  
       a light detector spaced apart from said at least one light source and being sensitive to intensity levels of said reflected light for producing intensity signals in accordance therewith; and  
       a processing unit for processing said intensity signals received from said light detector, said processing unit comprising:  
       first and second amplifiers for amplifying said intensity signals, each in accordance with a respective first and second gain amplification factor; and  
       a processor for automatically determining said first and second gain amplification factors in adjustable fashion;  
       wherein during a first stage, said first and second amplifiers amplify a DC signal component of said intensity signals in accordance with predetermined first and second gain amplification factors, and wherein the amplified DC signal component is subtracted from the intensity signals by a digital to analog converter and is subtracted from said intensity signals at an input of said first amplifier, to isolate an AC signal component of said intensity signals,  
       and wherein during a second stage, said second amplifier amplifying said isolated AC signal component in accordance with said adjustably-determined second gain amplification factor, said processing unit producing output signals in accordance with said isolated AC signal component and said DC signal component and calculating in accordance therewith, said level of oxygen saturation.  
     
     
       57. The method according to  claim 56 , wherein the processing is a serial process. 
     
     
       58. The method according to  claim 56  wherein said organ is the skin. 
     
     
       59. The method according to  claim 56  wherein said at least one extremum data value is selected from a minimum data value a maximum data value. 
     
     
       60. The method according to  claim 56  or  57  wherein said organ is an internal organ and wherein said method further includes the step of repeating said steps of providing light, providing a light detector and processing, at a plurality of positions along the surface of said internal organ for mapping levels of said AC signal component along the surface of said internal organ to detect regions of reduced blood